Hypodermic syringes are widely used in the field of medicine for withdrawing body fluids for tests or for delivering medicine to the body. Syringes are supplied in sterile condition and are normally intended for only a single use, in order to avoid any risk of contamination. The reuse of syringes, even those expected to go through a sterilization protocol, was favorable for the spreading of very serious infectious diseases such as AIDS or Hepatitis-B. The use of single-use sterilized hypodermic syringes overcame most of these risks because hospital personnel reliably disposed of the syringes after use.
A more dangerous situation occurs in the multiple use of syringes outside of the hospital where illegal drugs are injected in non-sanitary conditions. Under these circumstances, hypodermic syringes may be used on multiple occasions among several persons. This improper usage led to the spread of infectious diseases among the illegal drug-utilizing population. In order to reduce these risks, it is desirable to provide a syringe which disconnects the piston from the plunger after a single-use cycle.